This is a good question. Here is a brief timeline.
Adolf Hitler came to power in 1933. This is when the genocide of the Jews began to take shape. In that same year the Dachau concentration opened and the Germans began to boycott Jewish businesses. As the years passed by, the persecution of Jews became even greater. In 1935 the Nuremberg Race laws were introduced. In November of 1941, Einsatzgruppen killed 13,000 Jews from the Minsk ghetto, and this was only the beginning.
Elie Wiesel was born on September 30, 1928, in Sighet, a small town in Transylvania, which later became a part of Hungary. The Germans persecuted the Hungarian Jews in 1944. Eventually they killed over a half of a million Hungarian Jews. When Wiesel was fifteen, his family and friends of Sighet were led to Auschwitz in cattle cars.
In Auschwitz alone more than a million Jews died. Wiesel alone survived in his family and he finally emigrated to France.
Based on these points, we can say Wiesel experienced the full brunt of the genocide. During this time, the Germans were committed to their "final solution."